Note: There are other variables which are defined relative to this one. If you redefine this in your LocalSettings.phpManual:LocalSettings.php then all dependent variables including $wgUploadPathManual:$wgUploadPath will need redefining also. If both these settings are not coherent the files will be uploaded to different folder ($wgUploadDirectory) than from where MediaWiki will try to retrieve it for viewing ($wgUploadPath)!